Conventionally, there has been known a twin-lens three-dimensional display device that realizes three-dimensionality (3D) by preparing a left-eye image and a right-eye image, which form binocular parallax (refer to FIG. 22A), and independently projecting the left-eye image and the right-eye image on a left eye and a right eye of a viewer, respectively. According to such display method, a stereoscopic effect (pop-up amount) varies depending on the binocular parallax, that is, the amount of deviation between the left-eye image and the right-eye image. For example, as illustrated in FIGS. 22B and 22C, as the amount of deviation between left and right images becomes large, directions of left and right eyes viewing the image are apart from each other, resulting in a crossed position of both visual lines more distant from a screen. That is, as the amount of deviation of the left and right images becomes larger, a 3D image is displayed at a position further from the screen. As a result, the pop-up amount of the 3D image becomes large. For this reason, by calculating the amount of deviation between the left and right images and using the amount, the stereoscopic effect may be controlled, and discomfort in viewing the 3D image may be mitigated.
The amount of deviation between the left and right images is calculated, for example, by a block matching method using a sum of absolute difference of luminance signals as a standard (for example, refer to Japanese Laid-Open Patent Publication Nos. 2009-129420 and 2001-045523). According to the block matching method, as illustrated in FIG. 23A, a block BR1 of given size, which is cut from one image (here, right-eye image), is compared with a block BL1 of the other image (here, left-eye image), which is located at the same pixel, to calculate a sum of absolute luminance difference (SAD) between the pixel in the block BR1 and the pixel in the block BL1. Subsequently, as illustrated in FIG. 23B, the compared block BL1 of the left-eye image to be compared with the cut block BR1 is horizontally shifted one by one pixel and the SAD is calculated at each shift. As illustrated in FIG. 23C, the calculation of SAD (shift of the compared block BL1) is continued until the compared block BL1 reaches a terminal point of the left-eye image (a right end in FIG. 23C). Then, when the calculation of the SAD is completed at the terminal point of the left-eye image, as illustrated in FIG. 24A, the compared block BL1 corresponding to the minimum value of SAD among the calculated values of SAD is identified. The compared block BL1, which is identified as a region of the left-eye image that is the most similar to the cut block BR1, is associated with the cut block BR1. Then, a difference in horizontal coordinates between the position of the identified compared block BL1 and the position of the cut block BR1 is obtained as the amount of deviation between the left and right images (binocular parallax).
Next, as illustrated in FIG. 24B, the cut block BR1 is horizontally shifted by one pixel. Then, as described above with reference to FIGS. 23A to 23C, the compared block BL1 of the left-eye image is shifted one by one pixel to identify the position of the compared block BL1 corresponding to the minimum value of SAD, thereby calculating the amount of deviation between the left and right images. After that, as illustrated in FIG. 24C, the cut block BR1 is horizontally shifted one by one pixel until the cut block BR1 reaches a horizontal terminal point of the right-eye image (right end in FIG. 24C), and the amount of deviation between the left and right images is calculated each time the cut block BR1 is shifted.
Next, as illustrated in FIG. 25A, the cut block BR1 is returned to a horizontal start point of the right-eye image (a left end in FIG. 25A) and vertically shifted by one pixel. Then, as described above with reference to FIGS. 23A to 23C and FIGS. 24A to 24C, the amount of deviation between the left and right images is calculated. That is, each time the cut block BR1 is horizontally shifted by one pixel, the amount of deviation of the left and right images with respect to the cut block BR1 is calculated.
As illustrated in FIG. 25B, the above-mentioned processing is repeated until the cut block BR1 reaches the end point (lower right) of the right-eye image, and the amount of deviation of the left and right images is calculated at each cut block BR1.
However, according to the above-mentioned calculating method, since comparison operation (SAD calculation process) is performed with respect to all regions of the right-eye image and the left-eye image, as size of the left and right images becomes larger, processing time becomes longer.